Method for tempering saw blades, plane knives, and similar tools



Patented Mar. 13, 1928.

UNITED STATES 1,662,517 PATENT OF ICE.

PAUL HUSTADT AND KARL HUSTADT, OF REMSCHEID-HASTEN, GERMANY.

METHOD FOR TEMPERING SAW BLADES, PLANE KNIVES, AND SIMILAR TOOLS.

No Drawing. Original application filed July 10, 1923, Serial No. 650,691, and in Germany August 31, 1922. Divided and this application filed February 17, 1927. Serial No. 169,125.

-lhis invention aims to provide an improved method to be used in tempering and straightening thin cutting tools, such as circular and other saws, paper cutters, planeknives and the like, and to remove warping and irregularities of temper which have resulted form the previous steps of manufacture, without injuring the metal, to the end that the resulting product shall be of uniform character.

This application is a division of our copending application Serial No. 650,694 for method and machine for tempering saw blades, plane-knives and similar tools, filed J ulylO, 1923, to which reference is made for an illustrative embodiment of an apparatus capable of carrying out the method herein described. This apparatus is also illustrated in British Patent No. 218,822 of July 17,

In known tempering methods the-heating of the tools is. irregular due to the difficulty of controllingthe gas or coal fires generally used and the cooling is likewise irregular because there is no way of removing the entire article substantially instantaneously from the heat treating apparatus. These irregularities of treatment cause the tools to warp, which in turn necessitates a final straightening, generally accomplished by heating and hammering. This final straightening is applied only to the warped spots, causing irregularities of appearance and internal stresses, one result of which is that a saw may warp again after tooth cutting and setting, so-that the blade may have-to be straightened a second time.

The illustrative embodiment of the invention above referred to provides for simultaneous'tempering, setting and straightening of the tools by'pressing them between electrically heated plates, thermal and electrical measuring instruments being provided to permit close supervision of the heating throughout the treatment. Provision is also 7 made for. uniform cooling of the tools at the 'conchlsion of the treatment by causing all ortions of the tool to be simultaneously reeased from pressure and removed from the heat. e

Our method is particularly ap licable to previously-hardened tool blanks o the char-,

.acter set forth above. The blank to be treated is squeezed between electrically heat- 56 ed plates. As the blank yields under'the heat, the plates are gradually tightened together, thus flattening out irregularities of shape; At the same time, the internal stresses which caused such irregularities are removed, and the molecular structure becomes uniform throughout.

Furthermore, as the contact between the plates and the blank becomes closer, due to the straightening of warped spots, the transfer of heat from the plates to the blank becomes more effective, so that the gradual increase in pressure occasions in this way a gradual increase in the amount of heat effectively applied to the blank.

In our method the original hard temper of the blank is drawn tothe required degree, the amount of heat applied being appropriately regulated to accomplish this result. It is not within the purview of our invention to further harden the blank.

When the desired final temperature is reached, or when the treatment has continued the intended time, the entire area of both sides of the blank is instantaneously released from pressure, removed from contact with the hot plates and cooled in the air or otherwise. Bv such instantaneous release and removal all parts of the article are given identical treatment, thusassuring uniform molecular structure throughout, which in turn results in retention of the flat surface and the desired temper.

While our method is described" as applied to flat blanks, it will be obvious that the same principles may be employed in bringing blanksof other forms to final shape and temper.

We claim: 1. The method of tempering previouslyhardened saw blades, knives, cutters and 95 other thin articles which consists 1n simultaneously heating and pressing said articles to removeirregularities due to hardening by means of regularly and completely con.- trolled heat gradually applled and um- 10: formly difi'used.

2. The method of tempering previouslyhardened saw blades, knives, cutters and other thin articles which consists in heating said articles while maintained true toform under pressure toremove irregularities due to hardening by means of controlled heat difi'used with uniform intensity throughout the entire mass, followed by a sudden release of pressure and immediate uniform cooling. 110

3. The method of tempering and removing irregularities due to hardening from previously-hardened saw blades, knives, cutters and other thin articles, which consists in gradually and simultaneously applying to all parts of said articles uniform pressure and uniformly controlled evenly difiused heat, followed by substantially instantane ous release of said articles from said pres sure simultaneously with their removal from said heat.

4. The method of tempering and removing irregularities due to hardening from previouslyhardened saw blades, knives, cutters and other thin articles, which consists in gradually and simultaneously applying to all parts of said articles uniform ressure and uniformly distributed heat, 'ollowed by the simultaneous release of both sides of saidarticles.

5. The method of tempering and straightening previously-hardened saw blades, knives, cutters and other thin articles which consists in gradually and simultaneously applying to all parts of said articles uniform pressure and uniformly distributed heat, followed by the substantially instantaneous removal of the entire surface of said articles from said pressure and heat.

(3. The method of tempering and straightening previously-hardened saw blades, knives, cutters and other thin articles, which comprises simultaneously and progressively applying to said articles pressure and heat in evenly controlled amount and simultaneously releasing said ressure and removing said articles from sai heat.

7. The method of tempering and straightening previously-hardened saw blades, knives, cutters and other thin articles, which comprises simultaneously and progressively applying to said articles pressure and heat to a predetermined degree evenly diffused throughout said articles and thereupon simultaneously releasing said pressure and removing said articles from said heat to permit rapid uniform cooling of said articles.

8. The method of tempering previouslyhardened saw blades, knives, cutters and other thin articles which consists in slowly subjecting said articles to heat uniformly diffused throughout their mass simultaneously with the gradual application of pressure to said articles to remove irregularities of shape and of molecular structure which hate resulted from hardening, followed by substantially instantaneous cessation of heat and pressure treatment on all parts of both faces of said articles simultaneously.

9. The method of bringing a previouslyhardened thin metal article to final shape and to homogeneous molecular structure which comprises the gradual application of heat to a uniform distribution throughout said article concurrently with the squeezin of said article between plates of the desired form with gradually increasing pressure, followed by substantially instant and complete withdrawal of said article in its entirety from said heat treatment, simultaneously with the release of said pressure.

In testimony whereof, we have signed our names to this specification.

PAUL HUSTADT. KARL HUSTADT. 

